1. Technical Field
The present invention relates to a run flat tire.
2. Related Art
There is a pneumatic tire called a run flat tire that can run in a certain extent of distance even in the state that air pressure in a tire has reduced and reached 0 kPa by tire failure such as puncture. It is known to reinforce a side wall part by providing a side reinforcing rubber part on an inner surface of the side wall part as a technique for enabling run flat running in the state that an inner pressure has reduced as above (see US2006/0219343A1, US2012/0152425A1, JP-A-2001-080319 and JP-A-2010-132168).
In a run flat tire of such a side reinforcing type, high rigidity rubber is used in a side reinforcing rubber part to suppress deformation of a tire during run flat running. However, a temperature of a side reinforcing rubber part is increased during run flat running, and as a result, rigidity of the side reinforcing rubber part is decreased, resulting in decrease of run flat durability. Furthermore, where a high rigidity rubber is used in a side reinforcing rubber part and difference of properties between the side reinforcing rubber part and a bead filler as its adjacent member is increased, failure (for example, separation between a bead filler and a carcass ply) occurs in a bead part during run flat running, and run flat durability is sometimes decreased. Furthermore, fitting force to a rim is decreased during run flat running, thereby rim detachment in which a bead part detaches from a rim becomes easy to occur, and rim detachment resistance is sometimes decreased. Thus, a run flat tire sufficiently satisfying the level of marketing needs is not yet obtained.